import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
	public static void main(String[] args) {
		System.out.println("hello world");
		String s = "hello world";
		Book t = new Book("1");
		t.a();
		Ebook e = new Ebook("e", "e");
		e.zz();
		List<String> l = new ArrayList<>();
	}
}

class Book {
	String name;

	Book(String name) {
		this.name = name;
	}

	void a() {
		print(this.name);
	}

	void a(String s, String ss) {
		print(s);
		print(ss);
	}

	void print(String s) {
		System.out.println(s);
	}
}

class Ebook extends Book {
	String d;

	Ebook(String name, String d) {
		super(name);
		this.d = d;
	}

	void zz() {
		print(name + "e21");
	}
}
